The display technology develops rapidly and touch panels are widely used in daily life. Currently, depending on its structure, touch panels may be classified into add on mode touch panel, on cell touch panel and in cell touch panel. For the add on mode touch panel, the touch panel and a liquid crystal display (LCD) panel are produced separately, and then attached together so as to form an LCD panel having a touch function. However, the add on mode touch panel has such drawbacks as high manufacture cost, low light transmittance and large thickness. For the in cell touch panel, a touch electrode of the touch panel is built in the LCD panel so as to reduce an entire thickness of the panel and remarkably reduce its manufacture cost, so many manufacturers prefer the in cell touch panel.
The existing in cell touch panel detects a finger touching position based on mutual capacitance principle or self capacitance principle. In self-capacitive touch panel, multiple self-capacitive electrodes are arranged at the same layer and insulated from one another. When a human body does not touch the panel, the capacitance of each self-capacitive electrode is a fixed value. When the human body touches the panel, the capacitance of a corresponding self-capacitive electrode is a combination of the fixed value and the capacitance of the human body. Thus, a touch detection chip may determine a touch position by detecting a change of capacitance of each self-capacitive electrode at a touch stage. Since the capacitance of the human body may affect capacitances of all self-capacitive electrodes in the self-capacitive touch panel while the capacitance of the human body can only affect projected capacitance in a mutual-capacitive touch panel, capacitance change due to a touch operation of the human body on a self-capacitive touch panel can be greater than capacitance change due to a touch operation of the human body on a mutual-capacitive touch panel. Hence, the self-capacitive touch panel has enhanced signal-to-noise ratio of touch operation and improved accuracy of touch sensing when compared with the mutual-capacitive touch panel.
However, in practical use, the touch panel is pressed by a finger and deforms; hence, a distance between the self-capacitive electrode and a metal layer below the touch panel, such as a middle frame of a mobile phone, is decreased and capacitance between the self-capacitive electrode and the metal layer is increased accordingly. Such capacitance change is related to a finger pressure and is not a fixed value. As can be seen, such uncertain capacitance change is a noise interference for touch detection and may adversely affect the accuracy of touch sensing.